1. Field of the Invention
The present invention relates generally to manufacturing order planning and processing of orders for items containing a multitude of parts, and more specifically to computer systems to aid in the evaluation and interpretation of order information.
2. BACKGROUND
Manufacturing order planning is a significant problem in any industry producing and selling complex manufactured articles. The order planning process requires consideration of the types and models of a device that are expected to be ordered and shipped to customers. Each device may have a series of optional features or configurations that require different basic manufacturing parts or subassemblies.
Articles are typically sold to the customer by a sales person based upon a description of the basic model, optional devices, features and configurations. These descriptions must be in a form that is understandable by both the sales staff and customers. Such descriptions represent a level of abstraction that cannot be directly translated into a unmanfacturable product without an evaluation of the production rules governing model and device interactions. A manufacturing organization must be able to translate orders specified in terms of model and device codes into specific requirements for manufactured parts or assemblies. The end product of the manufacturing order planning process is a bill of materials that specifies detail, the parts necessary to fulfill the order. Long range planning is accomplished by analyzing hypothetical orders representing an expected configuration mix. A number of analyses may be performed based upon varied order configuration assumptions.
An actual or hypothetical order is converted into bills of material through consideration of engineering specifications and relationships documented by the manufacturing engineering staff. The engineers describe the relationships between the various models, features and components of a final assembled article. The requirements of the final assembly are interdependent such that a particular feature or option may require yet another feature to be added to the order. System constraints may be specified by stating that no more than a given number of a particular device may be added or, that at least a certain number of one type of device must be present in the final assembly.
The process of "exploding" the order into the final bill of materials has traditionally been a difficult, labor intensive process that relies upon the experience of the manufacturing engineers in relating the specifications to a production control group responsible for order processing. The field of Materials Requirement Planning (MRP) was developed to address this problem.
Computers were introduced into the order planning process to deal with the complexity of the interrelationships between the features specified in an order. Batch processed computer applications were developed that translate a particular order into the sub-assemblies and parts required for its assembly. However, the batch oriented computer systems lack the flexibility to easily adapt to changes in design. Once a detailed specification was developed for a batch system it was difficult to change or modify the specification to react to changes in the design of the product. Finally, validation of the bills of materials produced by batch systems is frequently difficult due to an inability to interact with the system.
The problem of difficult maintenance of relationships has been addressed through the use of knowledge based systems ("expert systems") that provide an ability to separate the rules specifying the relationship between components from the inference logic used to analyze the order and produce the bills of material. For example, a system called XCON has been used by the Digital Equipment Corporation to process and check orders for their computer systems. A particular customer's order is analyzed to determine whether or not that order is complete and whether additional components are required.
A refinement of the XCON system was developed by Teknowledge, Inc. and is described in U.S. Pat. No. 4,591,983 to Bennett et al. issued May 27, 1986. The system described in the patent to Bennett et al. provides for easy maintenance and analysis of the engineering relationships between orders and component parts. The system provides tools and access so additional rules can be added and relationships modified as necessitated by design changes.
The use of knowledge based systems provides an improvement in the process used to analyze orders and generate completed bills of material. However, prior art expert systems suffer from the limitation that an entirely new knowledge base must be constructed for each application. For example, the system described in the Bennett et al. patent was prepared using the LISP programming language. The use of a knowledge based system descriptor language such as LISP results in the order planning system having its own knowledge base that is distinct from and potentially inconsistent with existing production system data bases. In a large enterprise selling a large volume of products, a significant amount of engineering effort has gone into the development of a database or knowledge base describing the specifications and relationships between parts and components. Requiring a separate knowledge base for order planning purposes causes significant wasted effort in conversion and problems due to potential differences in the order planning and actual manufacturing phases of the manufacturing process.